SPIRAL GRAIN IN PLANTATION TREES OF PICEA-ABIES

The spiral-grain angle of Norway spruce (Picea abies (L.) Karst.) was measured on diametrical strips from five stands 23-47 years old, on soils of high and moderate fertility, most of which had been thinned heavily. Ninety-five small, average, and large trees from each stand were sampled from which 261 discs were sawn at heights ranging from 1.3 to 12 m. The basic pattern was typical for a conifer; spirality was left-handed in the inner annual rings, peaking in ring numbers 3 to 8, followed by a slow decline towards straight grain, or even right spirality, near the bark. The between-tree variation was statistically significant in all stands, with standard deviation near 1 degrees. A stand may exhibit a specific pattern of grain angle variation along the bole, but no variation with height in stem could be generally applied for Picea abies. For the three stands grown on fertile soils, the larger trees exhibited larger grain angles than the smaller trees. However, a consistent positive effect of ring width was only statistically significant for one stand. A subsample of 24 stem discs including 421 annual rings measured twice on two diametrical strips at right angles (i.e., crosses) showed fairly good accordance between the two directions, with a pooled standard deviation of 0.5 degrees. The results support earlier conducted studies with respect to complex and perplexing variations in the basic pattern of spirality typical for a conifer.